package string;

public class Demo06 {
    public static void main(String[] args) {
        String str = "Thinking in Java 是本好书!";
        String s = str.toUpperCase();
        //str.toUpperCase(); 转了之后没返回一个字符串,相当于买了车票不坐车
        String t = str.toLowerCase();
        System.out.println(s);
        System.out.println(str);
        System.out.println(t);
    }
}
